1. Field of the Invention
This invention relates to vortex flow meters and more particularly to an improved vortex meter for increasing the frequency of vortex shedding.
2. Description of the Prior Art
In the prior art in general a single bluff body is used upstream in the fluid flow of a sensor such as disclosed in U.S. Pat. No. 4,226,117, Herzl in which the sensor incidentally includes two parallel beams 12(a) and 12(b). Another Herzl U.S. Pat. No., 4,297,898 discloses a bluff body 11 and two parallel beams 13 and 14 downstream thereof on the front faces of which sensors are mounted.
U.S. Pat. No. 4,350,047, Dewey, Jr., et al. discloses two bluff bodies 14 and 16 positioned one behind the other in the direction of fluid flow with a sensor positioned in any location provided it or they sense the Karman vortices generated by coaction of the two cross members. The sensor can advantageously be located on or in the second cross member. It is noted that a single sensor is employed.
Colton U.S. Pat. No. 3,903,742 also employs two bluff bodies 17 and 19, one positioned downstream from the other, with the sensor in between, employed for measuring bidirectional flow such as the flow of air in and out of a person's lungs.
Japanese Patent No. 55-89756 Jul. 7, 1980 also discloses a pair of bluff bodies 2 and 3 employed for bidirectional measurement but incorporates two sensors 8 and 9 which also detect the direction of flow.
U.S. Pat. No. 3,564,915, Tomota, et al. in FIG. 21(a) also discloses two bluff bodies, one downstream from the other to provide a bidirectional vortex meter with a pair of separate sensors mounted on a pair of separate bluff bodies.
U.S. Pat. No. 3,927,566, Zanker, also shows in FIG. 7 two bluff bodies one downstream from the other for producing a flow switching in the gap therebetween. The sensors may be one or more heat loss detectors located on one or both of the bluff bodies. FIG. 8(a) shows two vortex members 111 and 112 connected by a member 115. Fluid flow is only in one direction and only the member 111 is connected to the wall of the conduit 114.
U.S. Pat. No. 4,485,679, Pitt et al., also discloses colinearly disposed bluff bodies 12 and 13 which interact with the fluid stream to generate vortices. Two detectors 14 and 15 are employed, one downstream of each of the bluff bodies and only unidirectional flow is disclosed.
The shortcoming of the prior art is that in the design of a large size vortex meter with a single bluff body installed in the middle the meter has low resolution which fact limits the application of vortex meters. The frequency is proportional to the flow velocity. The higher the frequency of vortex shedding, the smaller amount of gallons per pulse and accordingly, the higher the accuracy of the meter. When you use a large meter the frequency is small and so it is harder to get an accurate measure.
In accordance with an aspect of the present invention, it is an object to provide a new and improved vortex flow meter employing higher frequency of vortex shedding.
Another object is to provide a vortex fluid flow meter having a plurality of bluff bodies positioned perpendicular to the fluid flow optimized to cause the strongest vortex generation and to increase the frequency of vortex generation.